Lack of p38 activation in T cells increases IL-35 and protects against obesity by promoting thermogenesis

Obesity is characterized by low-grade inflammation, energy imbalance and impaired thermogenesis. The role of regulatory T cells (Treg) in inflammation-mediated maladaptive thermogenesis is not well established. Here, we find that the p38 pathway is a key regulator of T cell-mediated adipose tissue (AT) inflammation and browning. Mice with T cells specifically lacking the p38 activators MKK3/6 are protected against diet-induced obesity, leading to an improved metabolic profile, increased browning, and enhanced thermogenesis. We identify IL-35 as a driver of adipocyte thermogenic program through the ATF2/UCP1/FGF21 pathway. IL-35 limits CD8+ T cell infiltration and inflammation in AT. Interestingly, we find that IL-35 levels are reduced in visceral fat from obese patients. Mechanistically, we demonstrate that p38 controls the expression of IL-35 in human and mouse Treg cells through mTOR pathway activation. Our findings highlight p38 signaling as a molecular orchestrator of AT T cell accumulation and function.

(A-D) Female MKK3/6 CD4-KO and CD4-Cre mice were fed a high-fat diet (HFD) for 9 weeks (starting at 8-10 weeks old).(A) Body weight evolution in MKK3/6 CD4-KO and CD4-Cre female mice for 9 weeks.Data are presented as the increase above initial weight (left) and absolute weight at the end of the experiment (right).(B) MRI analysis of body and fat mass in MKK3/6 CD4-KO and CD4-Cre mice after 8 weeks of HFD.Representative images are shown on the right.(C) eWAT, sWAT, BAT, and liver mass relative to tibia length.(D) Skin temperature surrounding interscapular BAT.Right panels show representative infrared thermal images.Data Information: Data are presented as mean ± SEM, *p < 0.05, **p < 0.01, ***p < 0.001, ns: not significant.Analysis by 2-way ANOVA coupled to the Bonferroni post-test (A) or t test or by the Welch test when variances were different (A-D).n = 8-10 biologically independent mice for each group, represented as single dots in the graphs (A-D).Source data are available online for this figure.

EMBO reports
Ivana Nikolic et al

Figure EV3 .
Figure EV3.Lack of MKK3/6 in T improves adipose tissue metabolic homeostasis.(A, B) MKK3/6 CD4-KO and control CD4-Cre mice were fed an HFD for 8 weeks.qRT-PCR analysis of adipogenic, lipogenic, β-oxidation, and glycolytic genes mRNA expression from (A) eWAT and (B) sWAT isolated from control CD4-Cre or MKK3/6 CD4-KO mice.mRNA expression was normalized to the amount of b-actin mRNA.Data Information: Data are presented as mean ± SEM, *p < 0.05, **p < 0.01, ***p < 0.001, ns: not significant.Exact p values are shown.Analysis by t test or Welch's test when variances were different.n = 8-9 biologically independent mice for each group, represented as single dots in the graphs.Source data are available online for this figure.

Figure
Figure EV4.MKK3/6 deletion in T cells increases Treg cell population in blood and lymph nodes.
(A-C) MKK3/6 CD4-KO and CD4-Cre mice were fed a high-fat diet (HFD) for 8 weeks.FACS quantification and representative dot plots of CD4 + , CD8 + and Treg cells (CD4 + CD25 + Foxp3 + ) in spleen (A), blood (B), and lymph nodes (C).Data Information: Data are presented as mean ± SEM, *p < 0.05, **p < 0.01, ***p < 0.001, ns: not significant.Analysis by t test or Welch's test when variances were different.n = 7 biologically independent mice for each group, represented as single dots in the graphs.Source data are available online for this figure.

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Figure EV5.p38 MAPK pathway is upregulated in Treg cells in obese human adipose tissue.(A-G)The analysis was performed using human white adipose tissue single-cell RNA-seq data from Emont et al (Emont et al, 2022).(A) Dot plot of the expression of the indicated regulatory T cell (Treg) marker genes in the different cell type clusters.(B) Dot plot of the expression of the indicated genes by BMI range in human white adipose tissue Treg cluster shown in (A).(C) Violin plot showing the level of MAPK14 gene expression by BMI range in the human white adipose tissue Treg dataset.(D-E) Volcano plots of differentially expressed genes in human white adipose tissue Treg subcluster in obese (BMI 30-40 kg/m 2 ) versus non-obese (BMI 20-30 kg/m 2 ) subjects (D) and in severe obese (BMI 40-50 kg/m 2 ) versus non-obese (BMI 20-30 kg/m 2 ) subjects (E).(F) Violin plot showing the level of MAP2K3 gene expression by BMI range in the human white adipose tissue Treg dataset.(G) Volcano plots of differentially expressed genes in human white adipose tissue Treg subcluster in class 1 and 2 obesity (BMI 30-40 kg/m 2 ) versus non-obese (BMI 20-30 kg/m 2 ) subjects.The vertical dashed lines in (D, E, G) indicate a log2 fold change cut-off of 0.25.The horizontal dashed lines in (D, E, G) indicate a −log10 p-value cut-off of 1.3 (p-value < 0.05).Data information: Differentially expressed genes between BMI ranges were identified with a non-parametric Wilcoxon rank sum test.Obese (BMI 30-40 kg/m 2 ) N = 3 biologically independent patients; Severe obese (BMI 40-50 kg/m 2 ) N = 6 biologically independent patients; non-obese (BMI 20-30 kg/m 2 ) N = 5 biologically independent patients.DC: dendritic cells; Mac: macrophages; Mono: monocytes; Neu: neutrophiles; Mast: mastocytes.